Light and gravitational waves don't arrive simultaneously(bigthink.com)
bigthink.com
Light and gravitational waves don't arrive simultaneously
https://bigthink.com/starts-with-a-bang/light-gravitational-waves-arrive/
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Stellar event produces a gravity wave and a light pulse coincidentally at the source. As they travel through space together the gravity wave is compressing and expanding spacetime in the vacinity of the light pulse.
I could very easily believe that interaction by itself would be enough to have measurable effects over interstellar distances.
I could very easily believe that interaction by itself would be enough to have measurable effects over interstellar distances.
Yes. But our explanation should argue for the direction of difference (whether light arrives first or the gravity wave).
Aha! So the light pulse could be riding a kind of naturally-occuring Alcubierre warp bubble?
> In the mathematics of the physics, gravity is a scalar field.
No, it's a tensor field.
https://en.wikipedia.org/wiki/Riemann_curvature_tensor
No, it's a tensor field.
https://en.wikipedia.org/wiki/Riemann_curvature_tensor
Or only for the things that experience gravity as a curved surface?
Gravity, arguably, does not experience gravity as a curved surface.
Gravity, arguably, does not experience gravity as a curved surface.
How would you go about arguing that?
"Gravity as a fluid dynamic phenomenon in a superfluid quantum space. Fluid quantum gravity and relativity." (2015) https://hal.science/hal-01248015/
TLDR; In SQS (Superfluid Quantum Space), Quantum gravity has fluid vortices with Gross-Pitaevskii, Bernoulli's, and IIUC so also Navier-Stokes; so Quantum CFD (Computational Fluid Dynamics).
TLDR; In SQS (Superfluid Quantum Space), Quantum gravity has fluid vortices with Gross-Pitaevskii, Bernoulli's, and IIUC so also Navier-Stokes; so Quantum CFD (Computational Fluid Dynamics).
That article describes a hypothetical microphysical model of gravity. It's an old idea which has been done better by others (see e.g. "The Universe in a Helium Droplet" [1]). Whether right or wrong, it has no bearing on your claim that
> Gravity, arguably, does not experience gravity as a curved surface.
Any valid microphysical model of gravity must be able to reproduce the successes of general relativity in the classical limit, including the ability to match the shape of gravitational waves produced by black hole mergers. So if you want to argue that gravity "does not experience gravity as a curved surface", you have two options:
1) show that the non-linear (i.e. self-interaction) terms of Einstein's equations do not involve curvature or
2) come up with an alternative theory of gravity which does not reduce to general relativity in the classical limit and yet manages to reproduce all its successful predictions.
Which one is it?
[1] https://academic.oup.com/book/11557
> Gravity, arguably, does not experience gravity as a curved surface.
Any valid microphysical model of gravity must be able to reproduce the successes of general relativity in the classical limit, including the ability to match the shape of gravitational waves produced by black hole mergers. So if you want to argue that gravity "does not experience gravity as a curved surface", you have two options:
1) show that the non-linear (i.e. self-interaction) terms of Einstein's equations do not involve curvature or
2) come up with an alternative theory of gravity which does not reduce to general relativity in the classical limit and yet manages to reproduce all its successful predictions.
Which one is it?
[1] https://academic.oup.com/book/11557
[1] (2009) Does not disprove hydrodynamic SQS theories of quantum gravity.
A table of predictive error per experiment,{parameters},model might help us understand.
SQS purports to describe black hole internal topology where others do not. GR does not describe the internal topology of merging black hole vortices. Various theories of Quantum Gravity (QG) attempt to reconcile Dirac's pre-"Dirac sea" antimatter claims.
A unified model must: differ from classical mechanics where observational results don't match classical predictions, describe superfluid 3Helium in a beaker, describe gravity in Bose-Einstein condensate superfluids , describe conductivity in superconductors and dielectrics, not introduce unoobserved "annihilation", explain how helicopters have lift, describe quantum locking, describe paths through fluids and gravity, predict n-body gravity experiments on earth in fluids with Bernoulli's and in space, [...]
What else must a unified model of gravity and other forces predict with low error?
Why do I like Fedi's (2015/2016)? IDK. Maybe it's the abstract, maybe it's that nothing else even tries to do fluids and Bernoulli's. N-body gravity solutions with fluid vortices should predict all existing numerical n-body outcomes?
That so many things in space look fluidic - how many spiral arms are there on a nebula, all existing visual representations of black holes look like fluids, merging neutron stars look like emergent patterns from curl, too
Somehow I doubt anyone has even yet left an evolutionary algorithm online even all night to mutate and crossover the expression tree(s) to minimize predictive error according to existing experimental observations
A table of predictive error per experiment,{parameters},model might help us understand.
SQS purports to describe black hole internal topology where others do not. GR does not describe the internal topology of merging black hole vortices. Various theories of Quantum Gravity (QG) attempt to reconcile Dirac's pre-"Dirac sea" antimatter claims.
A unified model must: differ from classical mechanics where observational results don't match classical predictions, describe superfluid 3Helium in a beaker, describe gravity in Bose-Einstein condensate superfluids , describe conductivity in superconductors and dielectrics, not introduce unoobserved "annihilation", explain how helicopters have lift, describe quantum locking, describe paths through fluids and gravity, predict n-body gravity experiments on earth in fluids with Bernoulli's and in space, [...]
What else must a unified model of gravity and other forces predict with low error?
Why do I like Fedi's (2015/2016)? IDK. Maybe it's the abstract, maybe it's that nothing else even tries to do fluids and Bernoulli's. N-body gravity solutions with fluid vortices should predict all existing numerical n-body outcomes?
That so many things in space look fluidic - how many spiral arms are there on a nebula, all existing visual representations of black holes look like fluids, merging neutron stars look like emergent patterns from curl, too
Somehow I doubt anyone has even yet left an evolutionary algorithm online even all night to mutate and crossover the expression tree(s) to minimize predictive error according to existing experimental observations
>In 2017, such an event occurred
Negative. In 2017, such an event was observed.
Negative. In 2017, such an event was observed.
I’m going to be honest with you. I too used to be pedantic like this until one day I realized it’s really fucking annoying. Now let me tell you why you are wrong. :)
I’m fine with “occurred”. Because of causality the event had absolutely no impact on our local spacetime until those gravitational waves and photons showed up, regardless of how far back in time the event originated.
Another way to think about it: Because the photons and gravitational waves have no mass, no time occurred from their perspective between their origination point and arriving at earth.
I have no qualifications BTW. I just like physics. There’s a decent chance I’m wrong.
I’m fine with “occurred”. Because of causality the event had absolutely no impact on our local spacetime until those gravitational waves and photons showed up, regardless of how far back in time the event originated.
Another way to think about it: Because the photons and gravitational waves have no mass, no time occurred from their perspective between their origination point and arriving at earth.
I have no qualifications BTW. I just like physics. There’s a decent chance I’m wrong.
I believe that sentence is fine as the event in question is the lagging signals being observed.
> On August 17, 2017, the signal from an event that occurred 130 million light-years away finally arrived here on Earth.
> On August 17, 2017, the signal from an event that occurred 130 million light-years away finally arrived here on Earth.
So, it was observed but it did not occur? Could you expand this a little?
Bc of travel distance, meybe they mean that it occured earlier but observed than
It did not occur at the source of event, because at source gravitational waves and light waves were probably pretty close together, so "not simultaneous arriving of light and grav waves" is an event which was observed as happening on Earth in 2017.
Reddit.com is a different website.
Light and gravitational waves travel the same speed in a vacuum, but space isn’t really a vacuum. I wonder if this makes any contribution.
There are about 4.1e14 seconds in 130 million years. The two seconds delay is thus very small. I wonder what is the role of the fact that interstellar vacum is not an absolute vacum. I read some where that there is about one atom in each square cubic cm. The number of cm in one light year is 9.4605284e17.
Or just maybe light and gravitational waves are not created at the same time. Maybe just light is created 1.7s after.
How can we be so sure what happens in the physics of a kilonova that we suppose light and gw don't travel at the same speed ?
This seems intuitive, don’t photons have to interact with stuff and get dragged around by gravity and magnetic fields? I don’t think “gravitons” do that. Neutrinos can arrive before photons IIRC, simply because they don’t strongly interact.
Physics is wild.
Physics is wild.
In the mathematics of the physics, gravity is a scalar field. We don't really know what gravity is, we just have various descriptions that seem to be useful at various levels of detail. So when folks talk about gravity waves, in the maths it is a pulse traversing a scalar field, and we don't really know what is happening to the space or whatever it is that makes the pulse possible. Is space actually stretchy like elastic? Unknown. But it means that if there is no other potential field that can "bend" a moving gravitational wave's trajectory then gravitational waves will travel in absolutely straight lines.
Light, on the other hand, moves through the potentials generated by the gravity field and is governed by its energy, sort of, to follow geodesics of the gravity field. So in GR light takes the curvy path around objects with gravitational potentials around them. The article doesn't mention if there were any influential masses along the journey.
1.7 secs is about 320,000 miles. Maybe the curves?